Full runner electrolyzer stack for industrial-current-density NO<sub>x</sub><sup>-</sup>-mediated ammonia synthesis from air and water.

Liu, Wei; Lv, Yang; Ou, Honghui; Zhang, Jiqiu; Ren, Yuxi; Xia, Mengyang; Li, Yang; Li, He et al. · Nat Commun · 2025

basic_science · Level V

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Abstract

Plasma-electrochemical tandem conversion with NO<sub>x</sub><sup>-</sup> as intermediates promises a route for renewable ammonia (NH<sub>3</sub>) synthesis from air and water. However, a critical challenge lies in developing electrolyzers capable of operating efficiently at large current densities. Here, we present a scalable membrane electrode assembly electrolyzer with a full runner design (MEA-FR) that achieves efficient NH<sub>3</sub> production at industrial current densities. Compared to conventional serpentine runner configuration, MEA-FR leveraging forced convection within porous electrodes achieves three-order-of-magnitude enhancement in NO<sub>x</sub><sup>-</sup> mass transfer flux. This design, meanwhile, generates strong shear forces across the porous electrode, promoting rapid detachment of O<sub>2</sub> bubbles at the anode and reducing overpotential losses. Notably, MEA-FR exhibits a high Faradaic efficiency of 91.8 ± 1.4% for NH<sub>3</sub> synthesis at 500 mA cm<sup>-2</sup>, significantly outperforming the serpentine runner counterparts (64.9 ± 1.1%). Furthermore, a scaled-up 4 × 25 cm<sup>2</sup> MEA-FR stack with four modular cells is assembled with rotationally symmetric bipolar plates, delivering high NO<sub>x</sub><sup>-</sup> conversion efficiency (>95%), high Faradaic efficiency (>91%), and long-term stability (>200 h) under industrial-relevant current densities.